Some internal combustion engines utilize a compression device such as a turbocharger to increase engine torque/power output density. In one example, a turbocharger may include a compressor and a turbine connected by a drive shaft, where the turbine is coupled to an exhaust manifold side of an engine and the compressor is coupled to an intake manifold side of the engine. In this way, the exhaust-driven turbine supplies energy to the compressor to increase the pressure (e.g. boost, or boost pressure) in the intake manifold and to increase the flow of air into the engine. The boost may be controlled by adjusting the amount of gas reaching the turbine, for example with a wastegate. An actuator may be operatively coupled via a linkage to a wastegate valve and driven to position the wastegate valve anywhere between a fully open position and a fully closed position (e.g., at a valve seat) to achieve the desired boost based on operating conditions. The actuator may be an electric actuator such as an electric motor, for example.
In some scenarios, the electric motor may be exposed to high surrounding temperatures due to proximate flow of exhaust gasses, and may exhibit high temperatures itself, for example due to the continuous reception of high electrical currents—e.g., during operating conditions in which high or maximum boost is consistently desired. As such, estimation of the electric motor temperature may be desired to avoid degraded motor operation and degradation of the motor itself.
U.S. Pat. App. No. 2013/0312406 describes a method for controlling an electric actuator for a wastegate valve arrangement of an exhaust gas turbocharger. In particular, a temperature of the electric actuator may be estimated from an engine voltage supplied to the actuator, a battery voltage, and its operating current based on a calculation model.
U.S. Pat. No. 7,006,911 describes a system for estimating the temperature of an electric actuator. In one example, the electric actuator temperature is estimated based in part on a resistance temperature coefficient which represents a motor winding resistance.
The inventors herein have recognized several issues with such approaches. First, estimates of the temperature of an electric motor based on voltage supplied to the motor and its operating current may be inaccurate and in some scenarios may result in underestimating the temperature, which could lead to degraded motor operation and thus degraded boost control. The accuracy of motor temperature estimation in such an approach may be further reduced as other contributions to motor temperature are not considered, such as the surrounding environmental temperature due in part to proximate exhaust gas flow. Second, actions taken to prevent motor degradation may exceed what is necessary to ensure normal motor operation, such as reducing the current supplied to the motor by an excessive amount or ceasing current supply altogether, which may significantly reduce boost below a desired boost level and adversely impact the experience of a vehicle operator. Alternatively, the reduction of current supplied to the motor may be insufficient to avoid degraded motor operation.
Methods for controlling current supply to a wastegate actuator based on temperature are thus provided.
In one example, a method for operating a wastegate comprises limiting a boost amount in response to a current limit based on a temperature of a wastegate actuator.
In a more specific example, limiting the boost amount includes placing the wastegate actuator at a best possible position by supplying at most current equal to the current limit to the wastegate actuator.
In another aspect of the example, the temperature is an ambient temperature proximate the wastegate actuator.
In yet another aspect of the example, the method further comprises limiting a fuel amount supplied to an engine.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.